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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
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package sun.security.jca;

import java.util.*;

import java.security.*;
import java.security.Provider.Service;

List of Providers. Used to represent the provider preferences.
The system starts out with a ProviderList that only has the classNames
of the Providers. Providers are loaded on demand only when needed.
For compatibility reasons, Providers that could not be loaded are ignored
and internally presented as the instance EMPTY_PROVIDER. However, those
objects cannot be presented to applications. Call the convert() method
to force all Providers to be loaded and to obtain a ProviderList with
invalid entries removed. All this is handled by the Security class.
Note that all indices used by this class are 0-based per general Java
convention. These must be converted to the 1-based indices used by the
Security class externally when needed.
Instances of this class are immutable. This eliminates the need for
cloning and synchronization in consumers. The add() and remove() style
methods are static in order to avoid confusion about the immutability.
Author:
 Andreas Sterbenz
Since:
  1.5/**
 * List of Providers. Used to represent the provider preferences.
 *
 * The system starts out with a ProviderList that only has the classNames
 * of the Providers. Providers are loaded on demand only when needed.
 *
 * For compatibility reasons, Providers that could not be loaded are ignored
 * and internally presented as the instance EMPTY_PROVIDER. However, those
 * objects cannot be presented to applications. Call the convert() method
 * to force all Providers to be loaded and to obtain a ProviderList with
 * invalid entries removed. All this is handled by the Security class.
 *
 * Note that all indices used by this class are 0-based per general Java
 * convention. These must be converted to the 1-based indices used by the
 * Security class externally when needed.
 *
 * Instances of this class are immutable. This eliminates the need for
 * cloning and synchronization in consumers. The add() and remove() style
 * methods are static in order to avoid confusion about the immutability.
 *
 * @author  Andreas Sterbenz
 * @since   1.5
 */
public final class ProviderList {

    final static sun.security.util.Debug debug =
        sun.security.util.Debug.getInstance("jca", "ProviderList");

    private final static ProviderConfig[] PC0 = new ProviderConfig[0];

    private final static Provider[] P0 = new Provider[0];

    // constant for an ProviderList with no elements
    static final ProviderList EMPTY = new ProviderList(PC0, true);

    // dummy provider object to use during initialization
    // used to avoid explicit null checks in various places
    private static final Provider EMPTY_PROVIDER =
        new Provider("##Empty##", 1.0d, "initialization in progress") {
            private static final long serialVersionUID = 1151354171352296389L;
            // override getService() to return null slightly faster
            public Service getService(String type, String algorithm) {
                return null;
            }
        };

    // construct a ProviderList from the security properties
    // (static provider configuration in the java.security file)
    static ProviderList fromSecurityProperties() {
        // doPrivileged() because of Security.getProperty()
        return AccessController.doPrivileged(
                        new PrivilegedAction<ProviderList>() {
            public ProviderList run() {
                return new ProviderList();
            }
        });
    }

    public static ProviderList add(ProviderList providerList, Provider p) {
        return insertAt(providerList, p, -1);
    }

    public static ProviderList insertAt(ProviderList providerList, Provider p,
            int position) {
        if (providerList.getProvider(p.getName()) != null) {
            return providerList;
        }
        List<ProviderConfig> list = new ArrayList<ProviderConfig>
                                    (Arrays.asList(providerList.configs));
        int n = list.size();
        if ((position < 0) || (position > n)) {
            position = n;
        }
        list.add(position, new ProviderConfig(p));
        return new ProviderList(list.toArray(PC0), true);
    }

    public static ProviderList remove(ProviderList providerList, String name) {
        // make sure provider exists
        if (providerList.getProvider(name) == null) {
            return providerList;
        }
        // copy all except matching to new list
        ProviderConfig[] configs = new ProviderConfig[providerList.size() - 1];
        int j = 0;
        for (ProviderConfig config : providerList.configs) {
            if (config.getProvider().getName().equals(name) == false) {
                configs[j++] = config;
            }
        }
        return new ProviderList(configs, true);
    }

    // Create a new ProviderList from the specified Providers.
    // This method is for use by SunJSSE.
    public static ProviderList newList(Provider ... providers) {
        ProviderConfig[] configs = new ProviderConfig[providers.length];
        for (int i = 0; i < providers.length; i++) {
            configs[i] = new ProviderConfig(providers[i]);
        }
        return new ProviderList(configs, true);
    }

    // configuration of the providers
    private final ProviderConfig[] configs;

    // flag indicating whether all configs have been loaded successfully
    private volatile boolean allLoaded;

    // List returned by providers()
    private final List<Provider> userList = new AbstractList<Provider>() {
        public int size() {
            return configs.length;
        }
        public Provider get(int index) {
            return getProvider(index);
        }
    };

    
Create a new ProviderList from an array of configs
/**
     * Create a new ProviderList from an array of configs
     */
    private ProviderList(ProviderConfig[] configs, boolean allLoaded) {
        this.configs = configs;
        this.allLoaded = allLoaded;
    }

    
Return a new ProviderList parsed from the java.security Properties.
/**
     * Return a new ProviderList parsed from the java.security Properties.
     */
    private ProviderList() {
        List<ProviderConfig> configList = new ArrayList<ProviderConfig>();
        for (int i = 1; true; i++) {
            String entry = Security.getProperty("security.provider." + i);
            if (entry == null) {
                break;
            }
            entry = entry.trim();
            if (entry.length() == 0) {
                System.err.println("invalid entry for " +
                                   "security.provider." + i);
                break;
            }
            int k = entry.indexOf(' ');
            ProviderConfig config;
            if (k == -1) {
                config = new ProviderConfig(entry);
            } else {
                String className = entry.substring(0, k);
                String argument = entry.substring(k + 1).trim();
                config = new ProviderConfig(className, argument);
            }

            // Get rid of duplicate providers.
            if (configList.contains(config) == false) {
                configList.add(config);
            }
        }
        configs = configList.toArray(PC0);
        if (debug != null) {
            debug.println("provider configuration: " + configList);
        }
    }

    
Construct a special ProviderList for JAR verification. It consists
of the providers specified via jarClassNames, which must be on the
bootclasspath and cannot be in signed JAR files. This is to avoid
possible recursion and deadlock during verification.
/**
     * Construct a special ProviderList for JAR verification. It consists
     * of the providers specified via jarClassNames, which must be on the
     * bootclasspath and cannot be in signed JAR files. This is to avoid
     * possible recursion and deadlock during verification.
     */
    ProviderList getJarList(String[] jarClassNames) {
        List<ProviderConfig> newConfigs = new ArrayList<ProviderConfig>();
        for (String className : jarClassNames) {
            ProviderConfig newConfig = new ProviderConfig(className);
            for (ProviderConfig config : configs) {
                // if the equivalent object is present in this provider list,
                // use the old object rather than the new object.
                // this ensures that when the provider is loaded in the
                // new thread local list, it will also become available
                // in this provider list
                if (config.equals(newConfig)) {
                    newConfig = config;
                    break;
                }
            }
            newConfigs.add(newConfig);
        }
        ProviderConfig[] configArray = newConfigs.toArray(PC0);
        return new ProviderList(configArray, false);
    }

    public int size() {
        return configs.length;
    }

    
Return the Provider at the specified index. Returns EMPTY_PROVIDER
if the provider could not be loaded at this time.
/**
     * Return the Provider at the specified index. Returns EMPTY_PROVIDER
     * if the provider could not be loaded at this time.
     */
    Provider getProvider(int index) {
        Provider p = configs[index].getProvider();
        return (p != null) ? p : EMPTY_PROVIDER;
    }

    
Return an unmodifiable List of all Providers in this List. The
individual Providers are loaded on demand. Elements that could not
be initialized are replaced with EMPTY_PROVIDER.
/**
     * Return an unmodifiable List of all Providers in this List. The
     * individual Providers are loaded on demand. Elements that could not
     * be initialized are replaced with EMPTY_PROVIDER.
     */
    public List<Provider> providers() {
        return userList;
    }

    private ProviderConfig getProviderConfig(String name) {
        int index = getIndex(name);
        return (index != -1) ? configs[index] : null;
    }

    // return the Provider with the specified name or null
    public Provider getProvider(String name) {
        ProviderConfig config = getProviderConfig(name);
        return (config == null) ? null : config.getProvider();
    }

    
Return the index at which the provider with the specified name is
installed or -1 if it is not present in this ProviderList.
/**
     * Return the index at which the provider with the specified name is
     * installed or -1 if it is not present in this ProviderList.
     */
    public int getIndex(String name) {
        for (int i = 0; i < configs.length; i++) {
            Provider p = getProvider(i);
            if (p.getName().equals(name)) {
                return i;
            }
        }
        return -1;
    }

    // attempt to load all Providers not already loaded
    private int loadAll() {
        if (allLoaded) {
            return configs.length;
        }
        if (debug != null) {
            debug.println("Loading all providers");
            new Exception("Call trace").printStackTrace();
        }
        int n = 0;
        for (int i = 0; i < configs.length; i++) {
            Provider p = configs[i].getProvider();
            if (p != null) {
                n++;
            }
        }
        if (n == configs.length) {
            allLoaded = true;
        }
        return n;
    }

    
Try to load all Providers and return the ProviderList. If one or
more Providers could not be loaded, a new ProviderList with those
entries removed is returned. Otherwise, the method returns this.
/**
     * Try to load all Providers and return the ProviderList. If one or
     * more Providers could not be loaded, a new ProviderList with those
     * entries removed is returned. Otherwise, the method returns this.
     */
    ProviderList removeInvalid() {
        int n = loadAll();
        if (n == configs.length) {
            return this;
        }
        ProviderConfig[] newConfigs = new ProviderConfig[n];
        for (int i = 0, j = 0; i < configs.length; i++) {
            ProviderConfig config = configs[i];
            if (config.isLoaded()) {
                newConfigs[j++] = config;
            }
        }
        return new ProviderList(newConfigs, true);
    }

    // return the providers as an array
    public Provider[] toArray() {
        return providers().toArray(P0);
    }

    // return a String representation of this ProviderList
    public String toString() {
        return Arrays.asList(configs).toString();
    }

    
Return a Service describing an implementation of the specified
algorithm from the Provider with the highest precedence that
supports that algorithm. Return null if no Provider supports this
algorithm.
/**
     * Return a Service describing an implementation of the specified
     * algorithm from the Provider with the highest precedence that
     * supports that algorithm. Return null if no Provider supports this
     * algorithm.
     */
    public Service getService(String type, String name) {
        for (int i = 0; i < configs.length; i++) {
            Provider p = getProvider(i);
            Service s = p.getService(type, name);
            if (s != null) {
                return s;
            }
        }
        return null;
    }

    
Return a List containing all the Services describing implementations
of the specified algorithms in precedence order. If no implementation
exists, this method returns an empty List.
The elements of this list are determined lazily on demand.
The List returned is NOT thread safe.
/**
     * Return a List containing all the Services describing implementations
     * of the specified algorithms in precedence order. If no implementation
     * exists, this method returns an empty List.
     *
     * The elements of this list are determined lazily on demand.
     *
     * The List returned is NOT thread safe.
     */
    public List<Service> getServices(String type, String algorithm) {
        return new ServiceList(type, algorithm);
    }

    
This method exists for compatibility with JCE only. It will be removed
once JCE has been changed to use the replacement method.
Deprecated:
use getServices(List) instead/**
     * This method exists for compatibility with JCE only. It will be removed
     * once JCE has been changed to use the replacement method.
     * @deprecated use getServices(List<ServiceId>) instead
     */
    @Deprecated
    public List<Service> getServices(String type, List<String> algorithms) {
        List<ServiceId> ids = new ArrayList<ServiceId>();
        for (String alg : algorithms) {
            ids.add(new ServiceId(type, alg));
        }
        return getServices(ids);
    }

    public List<Service> getServices(List<ServiceId> ids) {
        return new ServiceList(ids);
    }

    
Inner class for a List of Services. Custom List implementation in
order to delay Provider initialization and lookup.
Not thread safe.
/**
     * Inner class for a List of Services. Custom List implementation in
     * order to delay Provider initialization and lookup.
     * Not thread safe.
     */
    private final class ServiceList extends AbstractList<Service> {

        // type and algorithm for simple lookup
        // avoid allocating/traversing the ServiceId list for these lookups
        private final String type;
        private final String algorithm;

        // list of ids for parallel lookup
        // if ids is non-null, type and algorithm are null
        private final List<ServiceId> ids;

        // first service we have found
        // it is stored in a separate variable so that we can avoid
        // allocating the services list if we do not need the second service.
        // this is the case if we don't failover (failovers are typically rare)
        private Service firstService;

        // list of the services we have found so far
        private List<Service> services;

        // index into config[] of the next provider we need to query
        private int providerIndex;

        ServiceList(String type, String algorithm) {
            this.type = type;
            this.algorithm = algorithm;
            this.ids = null;
        }

        ServiceList(List<ServiceId> ids) {
            this.type = null;
            this.algorithm = null;
            this.ids = ids;
        }

        private void addService(Service s) {
            if (firstService == null) {
                firstService = s;
            } else {
                if (services == null) {
                    services = new ArrayList<Service>(4);
                    services.add(firstService);
                }
                services.add(s);
            }
        }

        private Service tryGet(int index) {
            while (true) {
                if ((index == 0) && (firstService != null)) {
                    return firstService;
                } else if ((services != null) && (services.size() > index)) {
                    return services.get(index);
                }
                if (providerIndex >= configs.length) {
                    return null;
                }
                // check all algorithms in this provider before moving on
                Provider p = getProvider(providerIndex++);
                if (type != null) {
                    // simple lookup
                    Service s = p.getService(type, algorithm);
                    if (s != null) {
                        addService(s);
                    }
                } else {
                    // parallel lookup
                    for (ServiceId id : ids) {
                        Service s = p.getService(id.type, id.algorithm);
                        if (s != null) {
                            addService(s);
                        }
                    }
                }
            }
        }

        public Service get(int index) {
            Service s = tryGet(index);
            if (s == null) {
                throw new IndexOutOfBoundsException();
            }
            return s;
        }

        public int size() {
            int n;
            if (services != null) {
                n = services.size();
            } else {
                n = (firstService != null) ? 1 : 0;
            }
            while (tryGet(n) != null) {
                n++;
            }
            return n;
        }

        // override isEmpty() and iterator() to not call size()
        // this avoids loading + checking all Providers

        public boolean isEmpty() {
            return (tryGet(0) == null);
        }

        public Iterator<Service> iterator() {
            return new Iterator<Service>() {
                int index;

                public boolean hasNext() {
                    return tryGet(index) != null;
                }

                public Service next() {
                    Service s = tryGet(index);
                    if (s == null) {
                        throw new NoSuchElementException();
                    }
                    index++;
                    return s;
                }

                public void remove() {
                    throw new UnsupportedOperationException();
                }
            };
        }
    }

}